This proposal applies for the direct cost of acquisition of a single (5 watt) laser flow cytometer/cell sorter, with rapid data acquisition, additional data analysis computer system, and accessories for handling of viable samples and autocloning of sorted cells. A group of 7 major users with PHS peer-reviewed support is identified and requires 100% of the total usage of the instrument. Availability of flow cytometry at the University of Rochester is limited. Each of the 3 flow cytometer/cell sorters is in full-time use. Appropriate routine technical expertise is guaranteed by the commitment of the principal investigator and a trained technician. Additional technical expertise is available from a team of paid consultants. The commitment of the University of Rochester to continued support for the maximum productivity of the instrument is stated by the Senior Associate Dean of the Medical School. In addition, the Department of Pediatrics at the University of Rochester has guaranteed the annual operating budget for this instrument. Both this flow cytometer and the one proposed in a BRS Shared Instrumentation Grant application on the same date by Dr. James Leary, are necessary for the performance of the planned research of the two groups of user/investigators at the University of Rochester School of Medicine.